Weather seals for windows, doors and the like perform a highly useful function by conserving energy, avoiding drafts and maintaining uniform inside temperatures through the avoidance of heat loss. The weather seal is typically used between stationary and movable members; e.g., between a window frame and movable window.
To effect a proper seal over an entire area of contact, the weather seal should be both resilient and compliant. This avoids any potential problem with rough, irregular or uneven surfaces between the seal and the surface which it contacts.
Resilient weather seals are in common use today and are fabricated from a variety of materials, including foamed or cellular natural and synthetic materials, rubber or rubberized materials, vinyl-clad materials and resilient plastics.
One of the most useful weather seal materials are thermoplastic elastomers due to their high degree of resilience and compliance which is maintained over an extremely broad range of ambient temperatures. This range of temperatures encompasses the lowest outside winter temperatures to which we are exposed even in the coldest climates. Materials which do not have this advantageous characteristic become hard and brittle at lower temperatures, losing resilience and compliance and often times cracking or even breaking.
However, thermoplastic elastomers are not without disadvantages when used for weather seals. The material itself has a relatively high coefficient of static and dynamic friction, and as a result it is not generally suitable for applications where sliding movement takes place between stationary and movable members (e.g., sliding doors or hinged casement windows in which there is a wiping action). In applications such as these, the relative sliding movement between the weather seal and contact surface, which itself may also exhibit a high friction characteristic, will result in rapid wear and less than optimum operation (e.g., difficulty in closing the door or window).
Prior art structures have attempted to solve this problem in different ways. As an example, one structure utilizes a foamed, cellular core which is provided with an internal stiffener for purposes of strength in installation, and is then wrapped completely in a layer of vinyl. This composite structure provides good sealing capability at intermediate and higher temperatures, but the external vinyl layer becomes hard and brittle at lower temperatures. Under these circumstances, it loses its resilience and compliance, and at best it loses its capability to properly seal. At worst, the vinyl cracks or breaks, and as a result the device fails and must be replaced.
Equally as important due to its composite structure, the vinyl-clad weather seal is both difficult and expensive to manufacture, resulting in a higher cost to the ultimate consumer.
A second approach to the problem is evidenced in U.S. Pat. No. 3,385,001. The weather seal disclosed in this patent utilizes a rigid mounting section, a rigid rub strip spaced from the mounting section and a resiliently flexible diaphragm section disposed therebetween and joining the two. The rub strip is of a material such as polyvinylchloride, which has a relatively low coefficient of friction. However, the rub strip is necessarily rigid to perform its intended function, and as a result it has no resilience or compliance to effect a proper seal where irregular or rough surfaces are encountered.